Jan Bartek – AncientPages.com – A remarkable fossil discovery in the Grand Canyon has unveiled exceptionally preserved soft-bodied animals from the Cambrian period, offering an unparalleled view into early life over 500 million years ago.

Grand Canyon. Credit: Filio – Pixabay – Public Domain

Researchers have identified molluscs, crustaceans, and exotic worms with unique feeding adaptations, all preserved in a nutrient-rich “Goldilocks zone” that encouraged evolutionary experimentation. This find not only highlights the complexity of Cambrian ecosystems but also draws fascinating parallels between ancient biological innovation and modern economic risk-taking.

This treasure trove of early animals was discovered in one of nature’s most iconic sites—the Grand Canyon—and marks the first such find there. The fossils include tiny rock-scraping molluscs, filter-feeding crustaceans, spiky-toothed worms, and even fragments of their likely diet. By dissolving the rocks encasing these fossils and examining them under high-powered microscopes, researchers from the University of Cambridge have gained a detailed understanding of this unique period in Earth’s evolutionary history.

Dating back to between 507 and 502 million years ago during the Cambrian explosion—a time characterized by rapid evolutionary development when most major animal groups first appeared—these findings provide invaluable insights into life’s early complexity on our planet.

During this period, certain regions underwent an evolutionary arms race fueled by nutrient-rich waters, resulting in a diverse array of exotic adaptations in animals for feeding, movement, and reproduction.

While most Cambrian animal fossils are from hard-shelled organisms, unique sites like Canada’s Burgess Shale and China’s Maotianshan Shales have preserved softer body parts before decay could set in. Previously, non-skeletonized Cambrian fossils were primarily found in oxygen- and resource-poor environments that were not conducive to major evolutionary innovations. However, recent discoveries in the Grand Canyon have unveiled the first soft-bodied Cambrian fossils from an evolutionary ‘Goldilocks zone,’ rich with resources that likely accelerated early animal evolution.

Sternal elements of crustaceans from the Cambrian period. Credit: University of Cambridge

“These rare fossils give us a fuller picture of what life was like during the Cambrian period,” said first author Giovanni Mussini, a PhD student in Cambridge’s Department of Earth Sciences. “By combining these fossils with traces of their burrowing, walking, and feeding – which are found all over the Grand Canyon – we’re able to piece together at an entire ancient ecosystem.”

Mussini and colleagues from the US located the fossils during a 2023 expedition along the Colorado River, which began carving the Grand Canyon in what is now Arizona between five and six million years ago.

“Surprisingly, we haven’t had much of a Cambrian fossil record of this kind from the Grand Canyon before – there have been finds of things like trilobites and biomineralized fragments, but not much in the way of soft-bodied creatures,” said Mussini. “But the geology of the Grand Canyon, which contains lots of fine-grained and easily split mud rocks, suggested to us that it might be just the sort of place where we might be able to find some of these fossils.”

The researchers transported several rock samples back to Cambridge for analysis. Initially, these fist-sized rocks were dissolved in hydrofluoric acid, allowing the sediment to be sifted through multiple sieves and revealing thousands of tiny fossils. Although no complete animals were preserved, many identifiable structures enabled the researchers to determine the groups to which these animals belonged.

Further analysis of these fossils uncovered sophisticated evolutionary adaptations from the Cambrian period that animals used for capturing and consuming food. According to Mussini, “These were cutting-edge ‘technologies’ for their time, integrating multiple anatomical parts into high-powered feeding systems.”

Credit:  Joe Clevenger

Many of the fossils belong to crustaceans, likely related to brine shrimp, distinguished by their molar teeth. These small creatures possessed hair-like extensions on triangular grooves around their mouths and utilized hairy limbs like a conveyor belt to gather passing food particles. The grooves on their teeth facilitated grinding up food. The fossil details are so precise that several plankton-like particles can be observed near the crustaceans’ mouths.

Additionally, other modern-looking Cambrian animals found in the Grand Canyon include slug-like molluscs. These creatures already had belts or chains of teeth similar to those found in modern garden snails, likely aiding them in scraping algae or bacteria from rocks.

Researchers have identified a particularly unusual creature: a new species of priapulids, commonly referred to as penis or cactus worms. These creatures were prevalent during the Cambrian period but are now nearly extinct. The Grand Canyon priapulid is notable for its hundreds of complex branching teeth, which it used to gather food particles into its extensible mouth. Due to the fossil’s size and distinctive rows of teeth, researchers named this new species Kraytdraco spectatus, drawing inspiration from the krayt dragon, a fictional creature in the Star Wars universe.

“We can see from these fossils that Cambrian animals had wide variety of feeding styles used to process their food, some which have modern counterparts, and some that are more exotic,” said Mussini.

During the Cambrian period, the Grand Canyon was situated much closer to the equator, providing ideal conditions for a diverse array of life forms. The water’s depth was optimal—neither too deep nor too shallow—allowing for a balance that maximized nutrient and oxygen availability while minimizing wave damage and UV radiation exposure.

A newly discovered species of priapulids, commonly referred to as penis or cactus worms, has been identified. These creatures were prevalent during the Cambrian period but are now nearly extinct. The Grand Canyon priapulid is notable for its hundreds of complex branching teeth, which facilitated the sweeping of food particles into its extendable mouth. Due to the fossil’s size and distinctive rows of teeth, researchers have named this new species Kraytdraco spectatus, drawing inspiration from the krayt dragon—a fictional creature from the Star Wars universe. Credit: Rhydian Evans

This environment fostered evolutionary experimentation, as abundant food resources enabled animals to take evolutionary risks to outcompete others. This accelerated evolution and contributed to ecological innovations that continue to influence today’s biosphere.

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“Animals needed to keep ahead of the competition through complex, costly innovations, but the environment allowed them to do that,” said Mussini. “In a more resource-starved environment, animals can’t afford to make that sort of physiological investment. It’s got certain parallels with economics: invest and take risks in times of abundance; save and be conservative in times of scarcity. There’s a lot we can learn from tiny animals burrowing in the sea floor 500 million years ago.”

The study was published in the journal Science Advances

Written by Jan Bartek – AncientPages.com Staff Writer